Kristijan Posavec

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Mapping of soil moisture by time domain reflectometry and electrical resistivity tomography at Velika Gorica well field, Zagreb aquifer

Geofizika (2022)

Laura Bačani Kristijan Posavec Franjo Šumanovac Josipa Kapuralić

Knowing the soil moisture distribution in the unsaturated zone can improve understanding the water flow through the unsaturated zone and thereby enable the calculation of aquifer recharge, which occurs through precipitation. One part of the Zagreb aquifer recharge occurs through infiltration from precipitation. In order to observe and model infiltration from precipitation through the unsaturated zone, the research polygon was constructed at the Velika Gorica well field, located in the southern part of the Zagreb aquifer, Croatia, where hourly measurements of electric conductivity (EC) and soil moisture content were carried out. EC and soil moisture data are measured by Time Domain Reflectometry (TDR) probes which are placed at different depths in the unsaturated zone. Furthermore, electrical resistivity tomography (ERT) measurements were conducted. Geophysical data, along with moisture and EC data from TDR probes, were used as input data for MoisturEC software, in order to obtain soil moisture distribution along a 2D profile. MoisturEC program offers three options for translating EC data to moisture content data which are all tested in this research. We obtained eight moisture content distributions along the observed profile and concluded that MoisturEC provides reasonable results with input data from geophysical measurements and TDR probe measurements. Soil moisture distribution in the unsaturated zone represents the initial conditions for further unsaturated flow modeling. Understanding the flow in the unsaturated zone enables the quantification of effective infiltration and can improve groundwater management.

Infiltration (HVAC)

Electrical Resistivity Tomography

Reflectometry

10.15233/gfz.2022.39.13

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A Multi-Model Approach Using Statistical Index and Information Criteria to Evaluate the Adequacy of the Model Geometry in a Fissured Carbonate Aquifer (Italy)

Water (2016)

Marco Giacopetti Ezio Crestaz Marco Materazzi Gilberto Pambianchi Kristijan Posavec

A conceptual model related to a mountain aquifer that is characterized by a lack of data of hydrogeological parameters and boundary conditions, which were based on a single available observational dataset used for calibration, was studied using numerical models. For the first time, a preliminary spatial-temporal analysis has been applied to the study area in order to evaluate the real extension of the aquifer studied. The analysis was based on four models that were characterized by an increasing degree of complexity using a minimum of two zones and a maximum of five zones, which consequently increased the number of adjustable parameters from a minimum of 10 to a maximum of 22, calibrated using the parameter estimation code PEST. Statistical index and information criteria were calculated for each model, which showed comparable results; the information criteria indicated that the model with the low number of adjustable parameters was the optimal model. A comparison of the simulated and observed spring hydrographs showed a good shape correspondence but a general overestimation of the discharge, which indicated a good fit with the rainfall time series and a probably incorrect extension of the aquifer structure: the recharge contributes more than half of the total outflow at the springs but is not able to completely feed the springs.

Geostatistics

10.3390/w8070271

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Citations (6)

Laboratory determination of longitudinal dispersivity in Fluvisol

Stanko Ružičić Marta Mileusnić Kristijan Posavec Goran Durn

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Sixty years of global progress in managed aquifer recharge

Hydrogeology Journal (2018)

Peter Dillon Pieter J. Stuyfzand Thomas Grischek Mario R. Lluria R. David G. Pyne

The last 60 years has seen unprecedented groundwater extraction and overdraft as well as development of new technologies for water treatment that together drive the advance in intentional groundwater replenishment known as managed aquifer recharge (MAR). This paper is the first known attempt to quantify the volume of MAR at global scale, and to illustrate the advancement of all the major types of MAR and relate these to research and regulatory advancements. Faced with changing climate and rising intensity of climate extremes, MAR is an increasingly important water management strategy, alongside demand management, to maintain, enhance and secure stressed groundwater systems and to protect and improve water quality. During this time, scientific research—on hydraulic design of facilities, tracer studies, managing clogging, recovery efficiency and water quality changes in aquifers—has underpinned practical improvements in MAR and has had broader benefits in hydrogeology. Recharge wells have greatly accelerated recharge, particularly in urban areas and for mine water management. In recent years, research into governance, operating practices, reliability, economics, risk assessment and public acceptance of MAR has been undertaken. Since the 1960s, implementation of MAR has accelerated at a rate of 5%/year, but is not keeping pace with increasing groundwater extraction. Currently, MAR has reached an estimated 10 km3/year, ~2.4% of groundwater extraction in countries reporting MAR (or ~1.0% of global groundwater extraction). MAR is likely to exceed 10% of global extraction, based on experience where MAR is more advanced, to sustain quantity, reliability and quality of water supplies.

10.1007/s10040-018-1841-z

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Citations (459)

Method and Excel VBA Algorithm for Modeling Master Recession Curve Using Trigonometry Approach

Ground Water (2017)

Kristijan Posavec Marco Giacopetti Marco Materazzi Steffen Birk

Abstract A new method was developed and implemented into an Excel Visual Basic for Applications ( VBAs ) algorithm utilizing trigonometry laws in an innovative way to overlap recession segments of time series and create master recession curves ( MRCs ). Based on a trigonometry approach, the algorithm horizontally translates succeeding recession segments of time series, placing their vertex, that is, the highest recorded value of each recession segment, directly onto the appropriate connection line defined by measurement points of a preceding recession segment. The new method and algorithm continues the development of methods and algorithms for the generation of MRC , where the first published method was based on a multiple linear/nonlinear regression model approach (Posavec et al. 2006). The newly developed trigonometry‐based method was tested on real case study examples and compared with the previously published multiple linear/nonlinear regression model‐based method. The results show that in some cases, that is, for some time series, the trigonometry‐based method creates narrower overlaps of the recession segments, resulting in higher coefficients of determination R 2 , while in other cases the multiple linear/nonlinear regression model‐based method remains superior. The Excel VBA algorithm for modeling MRC using the trigonometry approach is implemented into a spreadsheet tool ( MRCTools v3.0 written by and available from Kristijan Posavec, Zagreb, Croatia) containing the previously published VBA algorithms for MRC generation and separation. All algorithms within the MRCTools v3.0 are open access and available free of charge, supporting the idea of running science on available, open, and free of charge software.

10.1111/gwat.12549

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Citations (19)

A combined approach for a modern hydrogeological mapping: the case study of Tennacola stream catchment (central Apennine, Italy)

Journal of Maps (2019)

Marco Giacopetti Marco Materazzi Gilberto Pambianchi Kristijan Posavec

ABSTRACT The current European water legislation, specifically the one addressed to groundwater for human consumption (EU Water Framework Directive, WFD-2000/60/EC), provides clear indications on the objectives and actions to be taken for the proper management and protection of water resources. In Italy, as well as in other countries of the EU, the implementation of this Directive, in the face of an adjustment of the legislation at national level, is still far behind, as regards the obligations on the part of local administrations. Among the reasons there is a lack of cognitive tools, adequate and, above all, univocally accepted by the scientific point of view. The hydrogeological mapping here presented, which covers an area of around 44 km2 and is edited at 1:10,000 scale, goes in this direction, combining different approaches and methodologies (field surveys, spring hydrograph analysis, surface flow measurements, numerical models …) to arrive at a complete and functional study of an aquifer exploited for drinking purposes.

Water Framework Directive

Directive

10.1080/17445647.2019.1574621

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Citations (3)

Water flow and solute transport model of potentially toxic elements through unsaturated zone at regional wellfield Kosnica

Stanko Ružičić Zoran Nakić Kristijan Posavec Marta Mileusnić Jelena Parlov

The subject of this study is the unsaturated zone in the area of the regional water wellfield Kosnica. The objective of this work was to build prognostic water flow model and potentially toxic element (lead, cadmium, zinc) transport model in the unsaturated zone. Research was conducted in the catchment area of the wellfield Kosnica, which is dominated by Fluvisol soil type. In order to better understand water flow and transport of potentially toxic elements in the unsaturated zone, detailed field and laboratory analyses and experiments were made. For numerical simulation HYDRUS-1D program was used. Program solves water flow using Richard's equation. Transport of potentially toxic elements is described with advection and dispersion equation. Based on laboratory analyses of soil properties, the parameters of water flow and solute transport were defined. Bulk density rises with depth while water holding capacity is the largest in the A horizon due to particle size distribution. Minimum values of hydraulic conductivity were determined in A and 4Cl/Cr horizons. Experimental results of sorption processes were used for determination of Freundlich sorption constants and exponents for individual elements. The minimum values of Freundlich's sorption constants and greatest exponents were determined in the first horizons for all three potentially toxic elements. Small differences in sorption were found between the individual elements. Based on chloride tracer experiments on soil columns in the laboratory, dispersivity was determined using Hydrus 1D inverse model. The dispersivity in AC horizon is 1 cm, and in C horizon is 1.7 cm. The correlation coefficient of the measured and simulated values of tracer concentration is 0.43 for AC horizon and 0.74 for C horizon. For the calibration of the water flow model, measured values of water content in the soil, using TDR probes for the period from 1/9/2011 to 31/10/2012, were used. Comparison of simulation results and measured water content was done. Simulated water content was less variable than the measured values. Low correlation (~0.40) coefficient between measured and simulated water content in the soil could be due to use of meteorological data from distant weather station. Hence, by using chloride tracer experiments on soil columns in the laboratory, calibration of the solute transport model was made. Using water flow and transport parameters, transport prognostic model of potentially toxic elements was created at the investigation site. Comparison of potentially toxic elements concentrations obtained by transport prognostic model at the bottom of the soil profile with their maximum allowed concentrations (MAC) limits ordinance indicate a high risk of groundwater contamination at the investigative site. However, it might be concluded that sorption processes have a major impact on the transport of potentially toxic elements in the unsaturated zone.

TRACER

Richards equation

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Analysis of mountain springs discharge time series in the Tennacola stream catchment (central Apennine, Italy)

Environmental Earth Sciences (2016)

Marco Giacopetti Marco Materazzi Gilberto Pambianchi Kristijan Posavec

10.1007/s12665-016-6339-1

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Citations (13)

Hydrogeological study for the quantification and protection of water resources (centralsouthern Marche)

Marco Giacopetti Domenico Aringoli Marco Materazzi Gilberto Pambianchi Kristijan Posavec

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Using Water Stable Isotopes and Cross-Correlation Analysis to Characterize Infiltration of Precipitation through Unsaturated Zone at the Velika Gorica Site of Zagreb Aquifer

Journal of Hydrologic Engineering (2023)

Zoran Kovač Laura Bačani Stanko Ružičić Jelena Parlov Kristijan Posavec

The unsaturated zone plays a crucial role in the hydrological cycle and is a key factor in modeling and understanding hydrological processes. It regulates water transfer from the land surface to the groundwater while providing protection, transfer, and attenuation of potential groundwater contaminants. This research presents the first results of continuous in situ monitoring of all soil horizons of the Eutric Cambisols and the remaining unsaturated zone of the Zagreb aquifer (Velika Gorica well field). The Zagreb aquifer is the main source of potable water for the inhabitants of the City of Zagreb and Zagreb County, which is protected by the Republic of Croatia. Cross-correlation analysis and water stable isotopes (δ2H and δ18O) were used to investigate whether there is a hydraulic connection between precipitation and groundwater, the approximate duration of percolation, and whether there are indicators that suggest the presence of preferential flow or processes such as water mixing and/or evaporation. The cross-correlation analysis showed and confirmed the assumption of the presence of preferential flow with average lag times ranging from 1.59 up to 3.63 h. The results also indicate that low organic matter content may contribute to higher lag times associated with precipitation infiltration. It was found that only high-intensity precipitation events allow effective infiltration, and that the amount of infiltration depends on the water content of the soil at the beginning of each precipitation event. The isotopic results showed that the isotopic composition of the soil water in the first three soil horizons follows the one of precipitation, while deuterium excess confirmed that the sampled water is mobile water and that an evaporation process is possible in the A horizon. The results also show that suction cups can be used to determine the isotopic signature of both bulk and mobile water, depending mainly on the granulometric composition of the material in which they are installed.

Infiltration (HVAC)

10.1061/jhyeff.heeng-5806

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Citations (5)